A rotor used for a compressor such as an axial flow compressor is securely fitted to a rotor shaft portion and thereby prevented from being displaced in the circumferential directions with respect to the rotor shaft portion when the axial flow compressor is in operation. For example, the following Patent Document 1 discloses that the fitting of a rotor and a rotor shaft portion is conducted by key coupling, tooth coupling or polygon fitting.
As given even in the following Patent Document 1, however, key coupling has a disadvantage in that a fitting hole may enlarge to thereby vibrate the rotor shaft portion. Tooth coupling or polygon fitting takes a great deal of time and labor for coupling working, thereby raising manufacturing costs.